5. Defining Classes and Their Hierarchies

These tools are suited for developing a class hierarchy from scratch, for adding classes to an application framework generated with AppExpress, and for browsing and editing pre-existing class hierarchies. They are especially useful for understanding the architecture of unfamiliar source code.

The Class and Hierarchy Editors can perform the same operations on classes and hierarchies; they differ only in their interface. The Class Editor's interface emphasizes member editing; the Hierarchy Editor's interface, through its graphical display, emphasizes inheritance relationships. Use one or the other, or both simultaneously, according to preference.

This chapter describes basic operations that may be performed with the Class and Hierarchy Editors. For a complete reference on these two tools, see Chapter 19, "Class Editor Reference", and Chapter 20, "Hierarchy Editor Reference".

Parsing and Browsing

To present you with a list of classes and members, the IDDE must parse the source code. By default, this is done automatically. When the IDDE detects that source code or project settings have changed since the last parse, it reparses the necessary files. If errors are encountered during parsing, messages are displayed in the Output window. You can double-click on the error message to open for editing the appropriate file at the point at which the error was detected.

How the class browsers expand macros

The parser treats an entire project as one "database" of code. Consequently, preprocessor macros defined in any header will expand in any subsequently parsed file. This can produce unexpected errors. For example:

	// foo1.h ------------------------------------
	#define pBar (pIndirect->pBar) 
	// . . .

	// foo1.cpp ----------------------------------
	#include <foo1.h> 


	// foo2.cpp ----------------------------------
	struct A 
	{   int *pBar;    // ERROR! Expands to: int * 
	    (pIndirect-> pBar);
	}; 

Browsing library source code

1. Choose Settings from the IDDE's Project menu.
2. In the Project Settings dialog box, click the Directories tab.
3. In the Browser Exclude Directories textbox, type the name of the directory containing the class library headers (for example, c:\dm\mfc\include).
4. Click OK.

Class Editor

To open a Class Editor window, do one of:

1. Choose Class Editor from the Window menu's Goto View submenu.
2. Click and drag the Class Editor icon from the Views toolbox to an empty area of the desktop.

1. The Classes pane, which contains a list of classes.
2. The Members pane, which contains a list of members of the current (highlighted) class.
3. The Source pane, which displays member source code. You can edit the source code in this pane as in the Source window (see Chapter 6, "Editing Program Code", for a description of text editing features).

[Figure 5-1 Class Editor window]

The Class Editor window contains a standard menu bar and toolbar; pop-up menus are available in each pane. You can set options for the grouping, sorting, and display of classes and members in the Classes and Members panes in the Editing/ Browsing Settings dialog box. For a complete reference on Class Editor menus and options, see Chapter 19, "Class Editor Reference".

You can change the relative sizes of panes in the Class Editor window by first positioning the cursor over the line separating the panes. The cursor changes to a two-headed arrow. Press the left mouse button and drag the separator to the desired location.

To select a class in the Classes pane, click on it. Additional classes may be selected by holding down the Control key and clicking. By default, classes are displayed hierarchically, with derived classes below and indented relative to their bases. Classes with multiple bases are displayed beneath each of the bases. Triangular buttons to the left of base classes can be used to collapse and expand branches of the hierarchy. You can set an option to display classes alphabetically in the Editing/ Browsing Settings dialog box.

By default, class members in the Members pane are grouped into Functions, Data, and Typedefs. The tree structure can be expanded or collapsed by clicking on the triangular buttons to the left of the category names. To select a class member, click on it. Additional members can be selected by clicking while holding down the Control key. You can display a member declaration or definition in the Source pane by double-clicking on the member name.

Creating classes

Creating a top-level class

To create a new top-level class:

1. Choose Add Top from the pop-up menu in the Classes pane. The Add Class dialog box is displayed (Figure 5-2).

   

   [Figure 5-2 Add Class dialog box]

2. Type a name for the new class.
3. Click OK.

Creating a derived class

To create a new derived class:

1. Select the base class of the new class.
2. Choose Add Derived from the pop-up menu in the Classes pane. The Create Derived Class dialog box opens. (This dialog box is similar to the Add Class dialog box.)
3. Type a name for the new class.
4. Click OK.

Creating a sibling class

To create a new sibling class:

1. Select the class whose base class will be the base class of the new class.
2. Choose Add Sibling from the pop-up menu in the Classes pane. The Create Derived Class dialog box is displayed.
3. Type a name for the new class.
4. Click OK.

Editing inheritance relationships

When altering inheritance relationships, the Class and Hierarchy Editors change only the class declarations. In particular, they do not change references to base classes and their members in a derived class's constructors or functions. If such references exist, you must change them manually in the source file.

Connecting to a base class

To make one existing class derive from another existing class:

1. Select the class that will be the derived class.
2. Choose Connect Base from the pop-up menu in the Classes pane. The Add Base dialog box opens (Figure 5-3).

   

   [Figure 5-3 Add Base dialog box]

3. From the listbox, select the class (or classes) to be this class's base class.
4. Select the desired access specifier. Check Virtual if virtual inheritance is desired.
5. Click OK.

Deleting a connection

To delete an inheritance relationship:

1. Select a derived class.
2. Choose Delete Base Connection from the pop-up menu in the Classes pane.
3. A message box requests confirmation. Click Yes to delete the base connection.

Editing inheritance attributes

To edit the base class access specifier:

1. In the Classes pane, select the derived class.

   In cases of multiple inheritance, select the base connection to edit by clicking on the instance of the derived class below the appropriate base.

2. Choose Edit Base Attributes from the pop-up menu in the Classes pane.

   The Edit Base Attributes dialog box opens (Figure 5-4).

   

   [Figure 5-4 Edit Base Attributes dialog box]

3. Select the desired access specifier. Check Virtual if virtual inheritance is desired. Click OK.

Working with class members

A list of the members of the currently selected class is shown in the Members pane (Figure 5-5). By default, the member list is sorted into three categories: Data, Functions, and Typedefs. Within each category, items are sorted alphabetically. The colored diamond in front of each member identifies the access as public (green), protected (yellow), or private (red). Names of members defined as macros appear in red.

Note: Members that appear in red are not syntactically verified before source changes are saved back to the file.

The lists following each category header can be collapsed or expanded by clicking on the triangular button to the left of the category name.

[Figure 5-5 Members pane of Class Editor]

Adding a class member

To add a class member:

1. Choose Add from the pop-up menu in the Members pane. The Add Member dialog box opens (Figure 5-6).

   

   [Figure 5-6 Add Member dialog box]

2. Type the member declaration. The member may be a data item (for example, int nCats), a function (for example, int NumCats()), or a typedef (for example, typedef int CATCOUNT). Do not type any storage specifiers into the declaration textbox; these are added by the Class Editor.
3. Select the desired access and storage specifiers. Check the Inline check box for an inline function.
4. Click OK.

By default, the first eight letters of the class name are used to derive the source filename for new functions. You may change the file name by entering an alternative name in the Source File textbox of the Add Member dialog box.

Deleting a class member

To delete a class member:

1. Select the class member to be deleted.
2. Choose Delete from the pop-up menu in the Members pane.
3. When the message box requests confirmation, click Yes to delete the member.

Changing member attributes

To change a member's access and storage specifiers:

1. Select the member you want to change.
2. Choose Edit Attributes from the pop-up menu in the Members pane. The Change Member Attributes dialog box opens (Figure 5-7).

   

   [Figure 5-7 Change Member Attributes dialog box]

3. Select the desired access and storage specifiers. Check the Inline check box for an inline function. Click OK.

If you are editing several members' attributes simultaneously and the access specifiers are not identical, a Don't Change option is displayed in the Access group box. Likewise, if the storage specifiers are not identical, a Don't Change option is displayed in the Storage group box. These options let you change other member attributes without affecting the original access or storage of each member. You may, however, select a particular access or storage specifier, and all members are given that attribute. Also, when you are editing several members' attributes, if the inline attributes are not the same, the Inline check box changes to allow three states (checked, unchecked, and grayed, indicating "Do not change") instead of the normal two-state options.

Viewing and editing member source

To view and edit member declarations and function definitions:

1. Double-click on the member in the Members pane.

   The member's declaration (for data items and pure virtual functions) or definition (for other functions) is displayed in the Source pane. If the source code is not available (as with MFC libraries, for example), the definition is displayed.

2. Click in the Source pane to begin editing. Editing operations here are identical to editing operations in other Source windows.
3. To save changes, choose Save from the pop-up menu in the Source pane.

Note: If you close the current project before you save a source file you've modified with the Class Editor, you cannot discard the changes or close the file until you reopen the project.

Viewing and editing source files

To view and edit the header file containing the class declaration:

1. Select the class in the Classes pane.
2. Choose Show Header from the pop-up menu in the Classes pane. A Source window containing the contents of the class header file is displayed.
3. Edit the class declaration as desired.

   You may add or delete class members as you would without the Class Editor. However, if you add functions to the declaration, you have to add the function definitions manually to the source file as well.

4. Save your changes by choosing Save from the Source window's File menu.
5. To close the Source window, choose Close from the File menu.
6. Click on the Class Editor window. If you have made changes to the header file, a message box asks whether it is OK to reparse. Click Yes.
7. Click on the class whose declaration you just edited to see the member changes updated in the Members pane.

To view and edit the source file containing member function definitions:

1. Select a member function from the Members pane.
2. Choose Show Source from the pop-up menu from the Members pane. (Show Source is dimmed if the source code is not available.)

   The file containing the member function's source code is opened for editing in a Source window.

3. Edit the member functions as desired.

   You may edit member functions as you would without the Class Editor. However, if you change function arguments or return types, or add new functions, you must modify or add the function declarations manually in the header file as well.

4. Save your changes by choosing Save from the Source window's File menu.
5. To close the Source window, choose Close from the File menu.
6. Click on the Class Editor window. If you have made changes to the source file, a message box asks whether it is OK to reparse. Click Yes.

Hierarchy Editor

To open a Hierarchy Editor window, do one of the following:

• Choose Hierarchy Editor from the Goto View submenu of the IDDE's Window menu.
• Double-click on the Hierarchy Editor icon in the Views toolbox, or drag the icon to an empty area of the desktop.

To enable the Hierarchy Editor child windows:

1. Choose Settings from the Hierarchy Editor's pop-up menu. The Editing/Browsing Settings dialog box opens to the Hierarchy page.
2. Check the items labeled Members and Source in the Pop-up Windows group box.
3. Click OK.

[Figure 5-8 Hierarchy Editor window]

Unlike the Members and Source panes of the Class Editor, Hierarchy Editor windows are independent. They have their own menus and may be positioned, sized, and closed separately. Otherwise, they behave as do the corresponding panes of the Class Editor. For a complete reference on Hierarchy Editor menus and options, see Chapter 20, "Hierarchy Editor Reference".

Creating classes

Operations relating to class creation and the establishment of hierarchical relationships are carried out in the Hierarchy Editor's graphical display window.

Creating a top-level class

To create a new top-level class:

1. Activate the Hierarchy Editor window.
2. Choose Add Top from the pop-up menu. The Add Class dialog box opens (Figure 5-9).

   

   [Figure 5-9 Add Class dialog box]

3. Type a name for the new class.
4. Click OK.

Creating a derived class

To create a new derived class:

1. Select the class that will act as the base class of the new class.
2. Choose Add Derived from the pop-up menu.

   You can also perform this step with the mouse. Hold the left mouse button down and drag the cursor from the selected class to an empty area of the window. A rubber band line appears as you do this (Figure 5-10). Release the mouse button.

   The Create Derived Class dialog box opens (this dialog box is similar to the Add Class dialog box).

   

   [Figure 5-10 Creating a new derived class using the mouse]

3. Type a name for the new class.
4. Click OK.

Creating a sibling class

To create a new sibling class:

1. Click on the class whose base class is to be the base class of the new class.
2. Choose Add Sibling from the pop-up menu. The Create Derived Class dialog box is displayed.
3. Type a name for the new class.
4. Click OK.

Editing inheritance relationships

In altering inheritance relationships, Class and Hierarchy Editors change only the class declarations, not references to base classes and their members in a derived class's constructors or functions. If such references exist, you must change them manually.

Connecting to a base class

To make an existing class a base of another existing class:

1. Click on the class that is to be the derived class.
2. Choose Connect Base from the pop-up menu. The Add Base dialog box opens (Figure 5-11).

   

   [Figure 5-11 Add Base dialog box]

3. From the listbox, select the class (or classes) that will be the derived class's base class.
4. Select the desired access specifier. Check Virtual if virtual inheritance is desired.
5. Click OK. The display changes to show the new inheritance relationship.

Deleting a connection

To delete an inheritance relationship:

1. Click on the line connecting the base and derived classes. The line is highlighted to show that it is selected (Figure 5-12).

   

   [Figure 5-12 Highlighted base-derived connection]

2. Choose Delete Base Connection from the pop-up menu.
3. When the message box requests confirmation, click Yes to delete the base connection.

Changing base class

To change a class's base class:

1. Click on the line connecting the derived class and its current base.

   The line is highlighted to indicate that it has been selected. Note that at the end nearest the base class, there is a small black box (referred to as the line's "handle").

2. Click on the line's handle. Holding down the left mouse button, drag the handle over the class that is to be the derived class's new base class.
3. When the message box requests confirmation, click Yes to change the base connection.

Editing inheritance attributes

To edit the base class access specifier:

1. Click on the line connecting the base and derived classes. The line is highlighted to show that it is selected.
2. Choose Edit Base Attributes from the pop-up menu. The Edit Base Attributes dialog box opens (Figure 5-13).

   

   [Figure 5-13 Edit Base Attributes dialog box]

3. Select the desired access specifier. Check Virtual if virtual inheritance is desired. Click OK.

Working with class members

A list of members of the currently selected class is displayed in the Members child window (Figure 5-14). By default, the member list is sorted into three categories: Data, Functions, and Typedefs. Within each of these categories, items are sorted alphabetically. The colored diamond in front of each member identifies the access as public (green), protected (yellow), or private (red). Lists following each category header can be collapsed or expanded by clicking on the triangular button to the left of the category name.

[Figure 5-14 Members child window]

Adding a class member

To add a class member:

1. Activate the Members child window.
2. Choose Add from the Member menu or from the pop-up menu. The Add Member dialog box opens (Figure 5-15).

   

   [Figure 5-15 Add Member dialog box]

3. Type the member declaration. The member may be a data item (for example, int nDogs), a function (for example, int NumDogs()), or a typedef (for example, typedef int DOGCOUNT). Do not type any storage specifiers into the declaration textbox; these are added by the Hierarchy Editor.
4. Select the desired access and storage specifiers. Check the Inline check box for an inline function.
5. Click OK.

By default, the first eight letters of the class name are used to derive the source file name for new functions. You can change the file name by entering an alternative name in the Source File textbox of the Add Member dialog box.

Deleting a class member

To delete a class member:

1. Select the class member to be deleted.
2. Choose Delete from the Member menu or from the pop-up menu.
3. When the message box requests confirmation, click Yes to delete the member.

Changing member attributes

To change a member's access and storage specifiers:

1. Select the member to be changed.
2. Choose Edit Attributes from the Member menu or from the pop-up menu. The Change Member Attributes dialog box opens (Figure 5-16).

   

   [Figure 5-16 Change Member Attributes dialog box]

3. Select the desired access and storage specifiers. Check Inline for an inline function. Click OK.

The class declaration in the header file is modified and the Members display is updated to reflect the changes.

Viewing and editing member source

To view and edit member declarations and function definitions:

1. Double-click on the member in the Members child window.

   The member's declaration (for data items and pure virtual functions) or definition (for other functions) is shown in the Source child window.

2. Click in the Source child window to begin editing. Editing operations here are identical to those in other Source windows.
3. To save changes, choose Save from the pop-up menu.

Viewing and editing source files

To view and edit the header file containing the class declaration:

1. Click on the class in the Hierarchy Editor window.
2. Choose Show Header from the pop-up menu.

   A Source window containing the contents of the class header file opens.

3. Edit the class declaration as desired.

   You may add or delete class members as you would without the Hierarchy Editor. However, if you add function declarations, you must add the function definitions to the source file manually as well.

4. Save your changes by choosing Save from the Source window's File menu.
5. To close the Source window, choose Close from the File menu.
6. Click on the Hierarchy Editor window. If you have made changes to the header file, a message box asks whether it is OK to reparse. Click Yes.
7. Click on the class whose declaration you just edited to see the member changes updated in the Members window.

1. Select a member function from the Members child window.
2. Choose Show Source from the Member menu or from the pop-up menu.

   The file containing the member function's source code is opened for editing in a Source window.

3. Edit the member functions as desired.

   You may edit member functions as you would without the Hierarchy Editor. However, if you change function arguments or return types, or add new functions, you must modify or add the function declarations manually in the header file as well.

4. Save your changes by choosing Save from the Source window's File menu.
5. To close the Source window, choose Close from the File menu.
6. Click on the Hierarchy Editor window. If you have made changes to the source file, a message box asks whether it is OK to reparse. Click Yes.